Induction system

ABSTRACT

Gasoline engine induction system for automobiles and the like provides less emission of undesirable exhaust products by having carburetor without an idle jet so that engine idles on a lean main jet with small enrichment arranged for idle as against offidle operation. Enrichment can be provided as by having the closing of the throttle open an external vent in the carburetor bowl, or by having a supplemental fuel jet opening in throttle barrel alongside idle position of downstream tip of throttle blade. Automatic choke can also be operated by mixture taken from downstream of carburetor venturi, heated, and delivered to thermally responsive choke actuator. Above features can be incorporated in a single small primary carburetor that is combined with one or two large secondary carburetors used for high power operation. Supplemental heating can be provided for mixture delivered by primary carburetor.

United States Patent [191 Bartholomew [451 Sept. 24, 1974 1 1 INDUCTION SYSTEM [75] Inventor: Earl Bartholomew, Birmingham,

[21] Appl. No.: 883,566

Related US. Application Data [63] Continuation-impart 0f Ser. No. 725,243, Jan. 29,

1968, Pat. NO. 3,523,680.

[52] US. Cl. 261/39 B, 261/23 A [51] Int. Cl. F02m 1/10 [58] Field of Search 261/23 A, 41.3, 39.1, 39.2,

261/41.4, 70, 72, 73, DIG. 67

[56] References Cited UNITED STATES PATENTS 1,368,178 2/1921 Maire 261/41 C 1,623,750 4/1927 3,180,576 4/1965 Herman 261/39 B 3,190,274 6/1965 Manning, Jr. et a1..... 261/39 B 3,298,677 l/1967 Anderson 261/41 D 3,307,837 3/1967 Winkler 261/50 A FOREIGN PATENTS OR APPLICATIONS 21,079 12/1919 France 261/41 C Primary ExaminerTim R. Miles 5 7 ABSTRACT Gasoline engine induction system for automobiles and the like provides less emission of undesirable exhaust products by having carburetor without an idle jet so that engine idles on a lean main jet with small enrichment arranged for idle as against off-idle operation. Enrichment can be provided as by having the closing of the throttle open an external vent in the carburetor bowl, or by having a supplemental fuel jet opening in throttle barrel alongside idle position of downstream tip of throttle blade. Automatic choke can also be operated by mixture taken from downstream of carburetor venturi, heated, and delivered to thermally responsive choke actuator. Above features can be incorporated in a single small primary carburetor that is combined with one or two large secondary carburetors used for high power operation. Supplemental heating can be provided for mixture delivered by primary carburetor.

1 Claim, 3 Drawing Figures 1 Ql k Stow PAIENIEUSEPEMSH 1 I I m I 111 1111111 IIIIIIIIIIIIILlIIIIIII/III 111111 1 I V I v a w jflitjfizplomew INDUCTION SYSTEM The present application is in part a continuation of U.S. Pat. application Ser. No. 725,243 filed Jan. 29, 1968, (now U.S. Pat. No. 3,523,680 granted Aug. 11, 1970 which in turn is a division of U.S. Pat. application Ser. No. 572,635 filed July 21, 1966, now U.S. Pat. No. 3,447,516 granted June 3, 1969. The lastmentioned application is a continuation-in part of U.S. Pat. applications Ser. No. 408,135 filed Nov. 2, 1964 (now U.S. Pat. No. 3,282,261 granted Nov. 1, 1966) and U.S. Pat. Ser. No. 443,956 filed Mar. 30, 1965 (now U.S. Pat. No. 3,310,045 granted Mar. 21, 1967). U.S. Pat. Ser. No. 408,135 is in turn a continuation-inpart of U.S. Pat. application Ser. No. 301,249 filed Aug. 12, 1963 (now abandoned) and U.S. Pat. Ser. No. 314,814 filed Oct. 12, 1963 (now U.S. Pat. No. 3,198,187 granted Aug. 3, 1965), while U.S. Pat. Ser. No. 443,956 is a continuation-in-part of said U.S. Pat. application Ser. No. 314,814 and of U.S. Pat. application Ser. No. 445,856 filed Mar. 29, 1965 (now U.S. Pat. No. 3,250,264 granted May 10, 1966).

The present invention relates to internal combustion engines of the type used to power vehicles such as automobiles. In operation the exhausts of such engines emit undesirable materials such as unburnt and partially burnt hydrocarbons and excessive carbon monoxide.

Among the objects of the present invention is the provision of novel induction systems for such engines, to help reduce their undesirable emissions.

The foregoing as well as other objects of the present invention will be more fully understood from the following description of several of its exemplifications, reference being made to the appended drawings in which:

FIG. 1 is a somewhat diagrammatic sectional view of a portion of an engine induction system pursuant to the present invention;

FIG. 2 is also a somewhat diagrammatic sectional view of a modified induction system representative of the present invention; and

FIG. 3 is a similar view of another induction system typical of the present invention.

According to the present invention an induction system for a gasoline engine has a venturi-containing air supply throat for providing suction to draw gasoline for operating the engine under part-throttle conditions with a combustion mixture having an air-to-fuel ratio at least as high as :1, said system having an automatic choke assembly including a gas conduit that draws a gaseous stream from the throat downstream of the venturi through an engine-heated stove to heat the gas and then cause it to heat up a temperature-responsive choke valve bias.

Such a construction is shown in FIG. 1 where an automatic choke control assembly 300 operates to bias a choke valve 302 toward a closed position during cold engine starting and warm-up. The choke valve 302 is connected through linkage 304 to an arm 305 fixed to one end of a rotatable shaft 303. The end of shaft 303 opposite the one connected to linkage 304 carries an arm 311 connected to a piston 312 loosely fitted in a pneumatic cylinder 313, and arm 311 has an extension 307 connected to a free end of bimetallic or similarly thermally-responsive coil spring 306, the other end of which is fixed and which is calibrated to resiliently urge the choke valve closed when the engine is cold. The coil is enclosed by a suitable housing 308 that defines a compartment 309 having an inlet port 310 connected to the outlet of a choke stove (not shown). The compartment 309 communicates with the cylinder 313 by way of the clearance around its loosely fitted piston 312, and the cylinder in turn has a longitudinally extending discharge port 315 leading to an intake manifold conduit 317.

The choke stove, which is conveniently mounted on the exhaust system, has an inlet running to a conduit 318 that opens at 320 inside thecarburetor throat in a direction that points upstream. Aside from this location of the choke stove inlet, the entire choke system can be of conventional construction, with the tension of the thermostatic coil 306, when cold, urging choke valve 302 closed until the engine is started and the air then entering the air horn 316 causes the valve which is unbalanced to open somewhat against the bias of the temperature-responsive thermostatic coil. At the same time intake manifold suction is applied by means of conduit 317 to the choke piston 312 and also tends to pull the choke valve 302 open.

The manifold suction also sucks gas from the compartment 309, causing some of the fuel-air mixture to be drawn from the carburetor throat through stove inlet 318. Heating of this mixture as it passes through the choke stove warms up the spring coil 306 so that it relaxes its tension.

As the engine warms up, the choke piston moves farther and farther to the right, as seen in FIG. 1, reducing but not completely cutting off the flow through the choke stove. This assures the maintenance of the spring coil 306 in fully warmedup condition during further operation of the engine.

By drawing the warm-up medium from the carburetor throat downstream of the venturi, the variations in warm-up flow of this medium with engine operating changes will not change the fuel-to-air proportion in the mixture delivered to the cylinders. All the air in such mixture must necessarily pass through the venturi (except for very slight leakage through throttle valve shaft journals or the like) so that the mixture can be more accurately metered. No excessive richening of the mixture is therefore needed to make up for the variable air leakage through the choke system ordinarily experienced where the choke stove inlet is upstream of the venturi.

The foregoing choke improvement is particularly effective where the carburetor venturi is used to provide idle combustion mixture as well as the combustion mixture for operating the engine at higher speeds and powers, that is off-idle. It will be noted in this connection that the construction of FIG. 1 has no idle fuel jet such as is conventionally used in engines. As explained in U.S. Pat. application Ser. No. 443,956, the idle fuel jet can be omitted where the venturi is made small enough to operate effectively with the low air flow rate developed at idle, and this is conveniently accomplished by having the throttle arranged to provide when closed a minimum mixture flow passageway with a crosssectional area at least about 6 to 10 percent that of its maximum passageway when wide open. As in that application the throttle plate in the construction of FIG. 1 can be perforated.

Inasmuch as the carburetor of FIG. 1 is, by reason of the absence of the usual idle mixture, readily adjusted to provide accurately proportioned fuel-air mixtures over the entire range of its operation, such adjustment can be made to give stoichiometric mixtures which result in extremely low exhaust emission. Leaner mixtures such as a 17:1 air fuel ratio will produce further reductions in exhaust emission and these leaner mixtures can be used in dual intake manifold systems such as described in U.S. Pat. application Ser. No. 408,135. Combining the carburetor structure of FIG. 1 with the fuel-cut-off features of US. Pat. Ser. No. 725,243 and if desired also adding a throttle-closing delay as described in the parent cases (now US. Pat. Nos. 3,282,261, 3,198,187 and 3,250,264) referred to in US. Pat. Ser. NO. 725,243, gives an extremely efficient induction system and one that has a strikingly low emission of carbon monoxide as well as of unburnt and partially burnt hydrocarbons.

For best operation the fuel-air mixture metered by the carburetor is preferably slightly richer at idle than under load. Such an arrangement enables smoother and more stable idling as compared to having the same mixture ratio for both types of operation.

In the construction of FIG. 1 a very small idle enrichment is provided by a vent 327 that opens to the atmosphere directly from the fuel bowl 314, when the throttle is in idle position, but is closed by flap 329 under all other throttle positions. When closed the fuel bowl is vented through vent tube 331 to the carburetor air horn 316 where the pressure is slightly below atmospheric during engine operation.

Flap 329 is shown as pivoted at 333 and as having a lever arm 335 biased upwardly by spring 337 to urge the flap toward vent-closing position. A soft gasket 339 below the flap helps assure effective vent closing. A link 341 connected between flap lever 355 and the throttle control is vertically recipr'ocable and is moved downwardly by a crank arm 343 mounted on the throttle shaft wnen the throttle moves into idle position, thus causing vent 327 to open. Opening of the throttle releases the link 341 and permits spring 337 to close the flap over the vent.

Vent 327 may also be made adjustable as by having flap 329 bendable to positions in which it partially blocks the vent even when the flap is lifted as far as it will go.

The extra idle enrichment of the present invention can be provided by other arrangements such as a very small idle port, and can amount to only a small fraction of an air-to-fuel ratio. The idle ratio can accordingly 14:1 with the operation ratio 15:1. In very warm climates however the idle mixture can be leaned down to 145:].

F IG. 2 shows a particularly desirable idle enrichment technique. In this figure a relatively small fuel port 382 is positioned within the throat 384 of a carburetor such as that of FIG. 1. The port opens into the throat alongside the downstream tip 388 of a throttle plate 390 suitably journaled in the induction passage. The plate is perforated as indicated at 386 to permit the passage of idle fuel mixture even though the plate is in fully closed position. During such idle operation a small amount of fuel is sucked into the throat from the fuel bowl 392 through the line 394 and the port 382. By locating the port opening alongside the downstream tip of the throttle plate below the upper edge of the tip and preferably as illustrated between the upper and lower edges of the tip, fuel flow through the port is cut off quickly whenever the throttle is opened even a small amount. As little as 5 of opening will leave the port effectively exposed to the ambient pressure above the throttle, which is not low enough to suck the fuel up from the fuel bowl.

Such a 5 limit on the enrichment operation is particularly desirable when operating with lean mixtures, that is mixtures having air-to-fuel ratios at least as high as 15:1. The idle enrichment is then essential to smooth idling so that the idling speed can be set to a relatively low value, generally not over 600 rpm, and the engine can then make full use of the fuel economy and low exhaust undesirables of the lean mixtures.

Permitting the enrichment to continue to 10 throttle opening (above idle) would carry the enrichment into a large portion of the engines low speed operations when used to power an automobile. Most present-day automobile engines are so powerful that in city traffic they need never have their throttle opened more than about 10.

The need for idle enrichment diminishes as the idle engine speed increases. At 700 rpm idle enrichment is still desirable but at 800 rpm it can be completely dispensed with.

As pointed out in the parent applications, the use of lean mixtures calls for a carburetor venturi of relatively small cross-sectional area. Thus for 16.5:1 mixtures (before idle enrichment) the venturi (or venturis where more than one is used) should have a combined crosssectional area at their minimum point of about 0.1 to 0.2 square inches per hundred total cubic inches displacement.

Although the port 382 of FIG. 2 may simply be a nonadjustable metered orifice in view of the very small amount of fuel it passes, it can be made adjustable by providing for, for example, a threaded screw 396 having a tapered end portion 398 that coacts with the port passageway to adjust its effective size. Additionally, the underside of the throttle plate may be recessed as at 399 to enable the port to be as high as possible and not have it obstructed too much by the throttle plate. A recess of this type is essential where the plate tip, instead of being rectangular, has its edge face tapered so that essentially the entire edge face engages the throat wall.

The line 394 is preferably provided with an air bleed so that the fuel supplied through the port 382 is in the form of an emulsion. Alternatively the bleed can be omitted and the port made somewhat smaller in crosssectional area.

Where the throttle plate is held open during idle, as for instance when the perforations 386 are not present, the enrichment port still preferably opens at a level between the upper and lower edges of the plate tip when the plate is in idle position. However the recessing of the lower face of the plate is then not needed.

The idle enrichment of the present invention only supplies a very small quantity of additional fuel. For example it enriches a mixture to 14:] from 15:1, so that the enrichment provides only about one-fourth of the idle fuel used. Where a separate port is used as the enrichment supply it is accordingly one with a very small cross-sectional area, much too small to be suitable for supplying all the idle fuel.

As shown in FIG. 1, the venturi-metered fuel is preferably introduced into the carburetor throat out of contact with the throat wall. This gives better operation with the lean mixtures of the present invention and also reduces the amount of idle enrichment and acceleration enrichment needed, as compared with a fuel discharge against the throat wall. A considerable lowering of the emission of undesirable exhaust products is accordingly obtainable when the fuel discharge is out of contact with the throat wall.

The choke and enrichment features of the construction of FIGS. 1 and 2 are particularly valuable when used together and also when used with primary carburetion barrels in a multiple carburetion system. Such an arrangement is shown in FIG. 3 which illustrates an intake manifold 400 for a V-8 engine, the manifold being equipped with a unitary three-barrel carburetor 410 having barrels 411, 412, 413. The combination is shown in sectional view, the section taken transversely of the engine crank shaft direction. The manifold has an upper wall 404 with three openings 40], 402, 403 very close together and they are shown as only separated by a sufficient amount to allow for locating securing bolts between them. They can be spaced even closer together by shifting the mounting bolts to other locations and can in fact be spaced apart as little as a half inch if desired, or even less. The space between the barrels is conveniently used to provide room for a common float chamber 320 so that this chamber can be essentially confined within the outer limits of the three barrels themselves. This greatly reduces the space occupied by the carburetor.

Mixture-receiving openings 401, 402, 403 are shown as opening downwardly into a transverse distributor section 405. Each transverse end may be branched to provide four outlets for the respective four cylinder intake ports at each bank of the V-8 engine. The usual heating duct cross-over between opposing exhaust ports in the two banks is shown as having branches 406, 407, branch 406 penetrating through distributor section 405 to provide more direct heating for the intake mixture passing through the section particularly from barrel 411. Branch 407 runs beneath the floor of distributor section 405 to provide further heating of the intake mixtures. Heating the fuel mixture in such a manner provides better distribution of the fuel to the engine. Heat-transfer ribs 408 can also be provided on the floor to further improve heat transfer.

Carburetor barrel 411 is the primary barrel on which the engine is operated under low power and cruising conditions, and it is relatively small as compared to the cross-sectional area made available by the intake manifold for carrying the mixture to all cylinders. As pointed out in U.S. Pat. application Ser. No. 408,135, a primary barrel with a venturi area only about onetenth that of the total venturi area when all carburetor barrles are in use, operates surprisingly well under partthrottle conditions with a mixture ratio of 16:1, which is leaner than heretofore considered practical. Such operation produced by hydrocarbon emission of only 112 parts per million in a standard V-8 engine that had its intake manifold modified to permit running on a small primary carburetor barrel with a venturi-throat-crosssectional area of 0.16 square inches per 100 cubic inches of total piston displacement. The manifold was originally of the standard two-barrel carburetor type and was modified by removing its common wall, a partition 1-7/16 inch deep by 1-% inch long known as the riser partition. Thus, the manifold was converted to one in which a common passageway branched to all cylinders. By contrast a standard four-barrel induction system on this engine produced hydrocarbon emission of dary, and each pair led through a longitudinal runner I and then through lateral branches to half the cylinders of the engine, two in each bank. The half not supplied by one runner was supplied by the other. The modification consisted of milling out a section 1-% inches deep by l-% inches long in the web between the manifold halves at the primary intake openings. A primary carburetor barrel was mounted over the center of the common chamber formed by this operation and the two secondary carburetor barrels were attached concentrically with the two secondary openings in the manifold. The primary carburetor had a venturi throat which was 15 percent of the combined cross-sectional area of the three venturi throats and 0.15 square inches per cubic inches of total piston displacement. A vehicle having an engine with this type of induction system has emitted only parts per million hydrocarbons and 0.4 percent carbon monoxide during a test commonly used to evaluate automible exhaust emissions, as opposed to 476 parts per million hydrocarbons and 2.7 percent carbon monoxide emitted by the same car with a standard induction system. The car with the modified induction system has proved to be driveable with mixture ratios of 17 pounds air per pound fuel.

In another embodiment a standard four-barrel manifold with two separate longitudinal runners was moditied to take three carburetors in a transverse arrangement. The partition between the two runners at the primary openings was milled away to a depth of 1 inch and separately outwardly directed lateral passageways were added to each longitudinal runner adjacent the intake openings, with a large secondary carburetor fitted on each lateral. The original secondary intake openings were covered and a primary carburetor fitted over the four intake openings. The roof of the heat cross-over for the standard manifold was used as a floor for the lateral passageways to provide a heated surface under each secondary carburetor.

The primary carburetor had a bore 1.1 inches in diameter and a venturi 0.88 inches in diameter, while the two secondary carburetors each had a bore l-% inches in diameter and a venturi 1-% inches in diameter. The primary venturi area was 0.12 of the combined crosssectional areas of the two longitudinal runners, and 0.16 square inches per 100 cubic inches of total piston displacement, which piston displacement corresponds to about 70 horsepower of maximum power output. The net venturi area of the primary carburetor was about 11 percent of the total net venturi area of the three carburetors.

The modified assembly operated very well with priof the foregoing secondary barrels is substituted for both of the secondary barrels in that combination. Such substitution is preferred for use with in-line engines such as the more conventional six-cylinder automobile engines inasmuch as it materially simplifies the induction system without detracting from its efficiency. On the other hand for V-type engines and particularly V-8s, it is preferred to have a pair of secondary barrels because they provide better induction and take up less space than a single larger secondary barrel.

The ratio of primary venturi area to total venturi area or to total cross-sectional area of manifold passageway can be as low as percent, and the primary venturi area can be as low as about 0.1 square inches for every 100 cubic inches of total piston displacement or for every 70 horsepower of maximum engine output, and still give very good operation, particularly with large engines such as used in large trucks and buses.

Increasing the relative size of the primary venturi beyond about 0.2 square inch for every 100 cubic inches of total piston displacement reduces the effectiveness of the operation with lean mixtures. At this proportion the primary venturi area is about /s the combined area of all venturis.

It is preferred that the primary barrel be so small that the air velocity through the most restricted portion of its venturi be about 200 to 300 feet per second when the engine is operating under road load cruise at 1,100 rpm. Conventional 4 barrel carburetors generally provide an air velocity of only about 60 feet per second in such operation.

Because of the relatively small size of the primary barrel as compared to the intake manifold dimensions, it is helpful to provide additional heating for the mixture supplied by that barrel. In FIG. 3 an extra shelf 406 is provided directly under opening 401, which shelf is the upper surface of the exhaust crossover 406. By having this shelf only about A to 1 inch below opening 401, fuel droplets delivered by barrel 411 will impinge directly on the shelf and volatilize as well as break up, to be carried away by the mixture movement with very little tendency to accumulate as a liquid pool on the floor of the manifold.

Instead of having the intake manifold arranged with its trunk passage or distributor section 405 running transversely of the engine, it could also run longitudinally of the engine as in conventional V-8 manifolds, with branches running to the individual cylinders from the longitudinal ends. With either arrangement it is preferred to have the throttle plates pivot about axes that are longitudinally directed, that is parallel to the crank shaft. Such an orientation gives better distribution of mixtures to the cylinders in both banks of the engine.

The fuel-metering arrangements of primary barrel 411 are essentially like those shown in US. Pat. applications Ser. No. 408,135 and Ser. No. 443,956, but the secondary barrels have auxiliary ports 472 that supply fuel when the secondary throttles are only slightly opened and not enough air is passed to operate their venturis.

The throttle of the primary carburetor barrel is also provided with a throttle-closing delay shown in FIG. 3 in the form of a dash-pot 470 that causes the throttle to close slowly in the event the throttle control is abruptly closed after the throttle-closing movement gets to the point that the air or mixture flow in the barrel reaches about 4/10 pound per hour per cubic inch displacement. The delayed rate of closure then can be about 5 to 10 percent per second, as described in US. Pat. Ser. No. 408,135, and the dash-pot construction can be the same as there described.

In addition, the throttle check is arranged to hold the minimum air flow rate somewhat above the idle limit for as long as possible, generally up to about 25 seconds after the beginning of a deceleration from about 50 miles per hour for an automobile driven by the engine of FIG. 3. The extra air of the mixture flow provided by the last few seconds of checking can be such that about 20 to 60 percent more flows through the barrel than the minimum for idling at no road load with 6 ignition advance before top center. After the throttle checking is completely terminated the throttle returns to the usual idle setting with the engine running at about 600 rpm or somewhat less, and the ignition timing about 6 before top center.

The constructions described above are particularly effective when used with automobiles having all mechanical transmissions, that is the type called manual. Such all-mechanical transmissions rigidly connect the engine to the automobile s wheels and such connections give the greatest concentration of undesired exhaust emissions during deceleration of the automobile. Automobiles that have fluid-coupled transmissions such as those called automatic, permit the engine to slow down much more abruptly than the vehicle does during deceleration and for this reason give much lower concentrations of undesirable exhaust emission during deceleration.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed:

1. An induction system for a gasoline engine, said system having a venturi-containing air supply throat for providing suction to draw gasoline for operating the engine under part-throttle conditions with combustion mixture having an air-to-fuel ratio at least as high as 15:1, said system having an automatic choke assembly including a temperature-responsive choke valve control, a stove, and a gas conduit having an inlet downstream of the venturi for drawing a gaseous stream from the throat through the stove to heat the gas and then cause it to heat up the temperature-responsive choke valve control. 

1. An induction system for a gasoline engine, said system having a venturi-containing air supply throat for providing suction to draw gasoline for operating the engine under part-throttle conditions with combustion mixture having an air-to-fuel ratio at least as high as 15:1, said system having an automatic choke assembly including a temperature-responsive choke valve control, a stove, and a gas conduit having an inlet downstream of the venturi for drawing a gaseous stream from the throat through the stove to heat the gas and then cause it to heat up the temperature-responsive choke valve control. 